1. Field of the Invention
The present invention relates to a method of manufacturing a magnetoresistive device including a magnetoresistive film pattern with a predetermined shape, a method of manufacturing a thin film magnetic head including such a magnetoresistive device disposed on a base, and a method of forming two or more thin film patterns with different sizes on a same base.
2. Description of the Related Art
In recent years, an improvement in performance of thin film magnetic heads has been sought in accordance with an increase in areal recording density of hard disk drives or the like. A magnetoresistive (hereinafter referred to as MR) head (MR head) including a MR device which is one of magnetic transducers is widely and commonly used as a reproducing head portion in the thin film magnetic head.
The examples of the MR device include anisotropic magnetoresistive (hereinafter referred to as AMR) devices using a magnetic film (AMR film) exhibiting an AMR effect, giant magnetoresistive (hereinafter referred to as GMR) devices using a magnetic film (GMR film) exhibiting a GMR effect and so on. A typical GMR device is a spin valve type GMR device, and the thin film magnetic head with a reproducing head portion using the spin valve type GMR device has been widely put to practical use.
Recently, the development of tunneling magnetoresistive (hereinafter referred to TMR) devices which have higher reproduction performance as compared with the spin valve type GMR devices, that is, can obtain a higher magnetoresistive ratio has been advanced. Signals stored in a recording medium having a smaller track width for high density recording can be reproduced by use of the TMR device.
In order to reduce variations in the reproduction performance of the MR head, it is required to reduce variations specifically in the dimensional accuracy of a MR height during patterning of the MR film. The MR height is a length (height) from an end on the side of a surface of the MR device facing the recording medium (air bearing surface) to the other end, and a polishing amount during processing of the air bearing surface determines the MR height.
Regarding the MR height, the applicant of the present invention has proposed a method of manufacturing a MR device capable of reducing variations in electromagnetic properties of the completed MR device and changes in the center of a distribution in electromagnetic properties of the completed MR device, and meeting predetermined specifications for magnetic reproduction in, for example, Japanese Unexamined Patent Application Publication No. 2001-006128. The method comprises the following steps.
First of all, a plurality of MR heads as well as a plurality of dummy resistive films which are thin film structures are formed on a base made of a material such as a ceramic, for example, through photolithography or the like. Then, the base is cut by use of a dicing saw or the like to form a plurality of bars each comprising a plurality of MR heads and a plurality of dummy resistive films.
Next, the plurality of bars obtained through the above step are set on a polishing apparatus or the like to mechanically polish their cut surfaces, that is, their air bearing surfaces. Mechanically polishing is not carried out while monitoring the dimension of the MR height, but while monitoring the electrical resistance of the dummy resistive films which have been already formed, in advance, on the bars. When the electrical resistance reaches a predetermined value, the polishing is stopped.
According to the above method, the processing accuracy of the MR height can be controlled, and variations in the properties of the MR device can be reduced to a certain point.
However, at present, a demand for higher density recording of hard disks, etc. has been further increased. Therefore, the adoption of a MR device using a MR film with higher sensitivity such as a TMR film has been studied, and a process of more accurately forming the dimension of the MR device applicable to a very small track width in the width direction has been in demand. It is difficult to satisfy the demands through patterning by use of the conventional photolithography, so the applicant of the invention has been pursuing the study of a method of patterning by use of electron beam (hereinafter referred to as EB) lithography.
Referring to FIGS. 37A through 42B, a method of forming a pattern when EB lithography is used in a method of manufacturing the MR device is described below. FIGS. 37A, 38A, 39A, 40A, 41A and 42A show plan views, and FIGS. 37B, 38B, 39B, 40B, 41B and 42B show cross sectional views taken along the line xxe2x80x94x. As shown in FIGS. 37A and 37B, first of all, a multilayer film 220A is formed through sputtering or the like on a base 210 on which an insulating layer (not shown) is disposed. Then, as shown in FIGS. 38A and 38B, an EB resist film 71 is formed on the multilayer film 220A. Next, as shown in FIGS. 39A and 39B, EB resist patterns 71A and 71B are selectively formed through EB lithography. The EB lithography is carried out through scanning areas where the patterns are formed while irradiating with an electron beam. After that, as shown in FIGS. 40A and 40B, the multilayer film 220A is selectively etched by use of the EB resist patterns 71An and 71B as masks through, for example, ion milling. Thereby, a MR film pattern 201 and a dummy resistive film pattern 202 are formed. Then, an insulating layer 72 is formed all over the area as shown in FIGS. 41A and 41B. After that, as shown in FIGS. 42A and 42B, the remained EB resist patterns 71A and 71B are removed through lift off processing, then the MR film pattern 201 and the dummy resistive film pattern 202 both having a predetermined planer shape and a predetermined size can be obtained.
Thus, by use of EB lithography, compared with the conventional photolithography, the MR film pattern 201 having a smaller dimension in the width direction can be accurately formed. However, on the other hand, much time is required to form the relatively large dummy resistive film pattern 202, resulting in worse throughput in the manufacturing process.
Moreover, relative displacement between the MR film pattern and the dummy resistive film pattern occurs due to the electrical charge on the base on which the patterns are formed. When the base carries an electrical charge unevenly depending upon areas, the electron beam is deflected at a rate depending upon areas on the base, thereby resulting in the occurrence of the relative displacement. As the electrical charge in this case varies depending upon areas on the same base as well as individual bases, the amount of the relative displacement varies, which leads variations in the relative displacement in the base as well as among the bases. Therefore, variations in dimensions occur when processing the MR height through mechanically polishing, thereby variations in the reproduction output of the MR head become larger.
In view of the foregoing, it is a first object of the present invention to provide a method of manufacturing a magnetoresistive device and a method of manufacturing a thin film magnetic head capable of efficiently forming a magnetoresistive device having an extremely small magnetoresistive film pattern.
It is a second object of the invention to provide a method of manufacturing a magnetoresistive device and a method of manufacturing a thin film magnetic head capable of reducing variations in dimensions of a magnetoresistive film pattern.
It is a third object of the invention to provide a method of forming a thin film pattern, and more specifically efficiently forming a plurality of thin film patterns with different sizes on a same base with accuracy according to each of the plurality of thin film patterns.
In a method of manufacturing a magnetoresistive device according to the invention, the magnetoresistive device includes a magnetoresistive film pattern with a predetermined shape, and the method comprises: a first step of forming a magnetoresistive film on a base; a second step of patterning the magnetoresistive film through at least electron beam lithography to form the magnetoresistive film pattern; a third step of forming a dummy resistive film on the base; and a fourth step of patterning the dummy resistive film through photolithography to form a dummy resistive film pattern used for reprocessing the magnetoresistive film pattern.
In a method of manufacturing a magnetoresistive device according to the invention, the magnetoresistive film formed on the base is patterned through at least electron beam lithography to form the magnetoresistive film pattern with a predetermined shape. On the other hand, the dummy resistive film formed on the base is patterned through photolithography to form the dummy resistive film pattern used for reprocessing the magnetoresistive film pattern. Electron beam lithography which selectively performs exposures by use of an electron beam in such a way as to draw lines allows more accurate patterning, compared with photolithography which selectively performs exposures by use of light, so at least a portion of the magnetoresistive film pattern where electron beam lithography is carried out can be patterned with higher accuracy, compared with the dummy resistive film pattern.
When the dummy resistive film pattern is larger in size than the magnetoresistive film pattern, a method of manufacturing a magnetoresistive device according to the invention is more preferably applicable. In this case, while the magnetoresistive film pattern with a smaller size is formed through electron beam lithography requiring a relatively long time for exposures, the dummy resistive film pattern with a larger size is formed through photolithography requiring a relatively short time. Therefore, according to the method, compared with the case where both of the patterns are formed through electron beam lithography, a time required for lithography can be reduced. On the other hand, compared with the case where both of the patterns are formed through photolithography, the forming accuracy of the magnetoresistive film pattern with a smaller size can be specifically improved.
When the magnetoresistive film pattern includes a first outline and a second outline, and the second outline requires higher processing accuracy than the first outline or has a smaller size than the first outline, a method of manufacturing a magnetoresistive device according to the invention is preferably applicable. In this case, while the first outline is formed through photolithography, the second outline is formed through electron beam lithography. Therefore, according to the method, electron beam lithography which is superior in patterning accuracy is used only for an outline specifically requiring higher processing accuracy, and photolithography is used for other outlines. Thereby, compared with the case where the whole magnetoresistive film pattern is formed through electron beam lithography, a time required for lithography can be further reduced.
In a method of manufacturing a magnetoresistive device according to the invention, it is preferable that the step of forming the first outline of the magnetoresistive film pattern and the fourth step are concurrently carried out. In this case, the first outline and the dummy resistive film pattern are concurrently formed through photolithography, so compared with the case where they are separately formed through photolithography, relative displacement between the first outline of the magnetoresistive film pattern and the dummy resistive film pattern can be reduced.
In a method of manufacturing a thin film magnetic head according to the invention, the thin film magnetic head includes a magnetoresistive device having a magnetoresistive film pattern with a predetermined shape disposed on a base, and the method comprises: a first step of forming a magnetoresistive film on the base; a second step of patterning the magnetoresistive film through at least electron beam lithography to form the magnetoresistive film pattern; a third step of forming a dummy resistive film on the base; a fourth step of patterning the dummy resistive film through photolithography to form a dummy resistive film pattern; and a fifth step of polishing a side surface of the base as well as an end surface of the magnetoresistive film pattern and an end surface of the dummy resistive film pattern to form a recording-medium-facing surface facing a recording medium, wherein the amount of polishing in the fifth step is controlled based on electrical resistance of the dummy resistive film pattern.
In a method of manufacturing a thin film magnetic head according to the invention, like the above-described method of manufacturing a magnetoresistive device, while the magnetoresistive film pattern is formed on the base through at least electron beam lithography, the dummy resistive film pattern is formed on the base through photolithography. As described above, electron beam lithography allows more accurate patterning, compared with photolithography, so a portion of the magnetoresistive film pattern where electron beam lithography is carried out can be patterned with higher accuracy, compared with the dummy resistive film pattern. Further, the end face of the magnetoresistive film pattern together with the side surface of the base are polished under the control based on the electrical resistance of the dummy resistive film pattern to form a completed recording-medium-facing surface. In other words, the magnetoresistive film pattern including at least a portion patterned with high accuracy is reprocessed (polished) so that a final dimension (height dimension) of the magnetoresistive film pattern in the direction orthogonal to the recording-medium-facing surface is controlled so as to become a predetermined value.
When the magnetoresistive film pattern has a strip shape determined by a dimension in the width direction defining a recording track width of a recording medium and a dimension in the height direction orthogonal to the width direction, and the dimension in the height direction is larger than the dimension in the width direction, a method of manufacturing a thin film magnetic head according to the invention is more preferably applicable. In this case, the dimension in the height direction is determined by patterning through photolithography, and the dimension in the width direction is determined by patterning through electron beam lithography. In other words, when determining the dimension in the height direction, photolithography is used, and when determining the dimension in the width direction which requires specifically high processing accuracy, electron beam lithography superior in lithography accuracy is used. Therefore, compared with the case where the whole magnetoresistive film pattern is formed through electron beam lithography, a time required for lithography can be further reduced.
In a method of manufacturing a thin film magnetic head according to the invention, it is preferable that a step of determining the dimension of the magnetoresistive film pattern in the height direction and the fourth step are concurrently carried out. In this case, a portion determining the dimension of the magnetoresistive film pattern in the height direction and the dummy resistive film pattern are concurrently formed through photolithography. Therefore, compared with the case where they are separately formed through photolithography, the relative displacement between the magnetoresistive film pattern and the dummy resistive film pattern can be reduced.
A method of forming a thin film pattern according to the invention comprises the steps of: forming a first thin film pattern on a base through at least electron beam lithography; and forming a second thin film pattern on the base through photolithography, the second thin film pattern being larger than the first thin film pattern.
In a method of forming a thin film pattern according to the invention, while the first thin film pattern with a smaller size is formed though electron beam lithography requiring a relatively long time for exposures, the second thin film pattern with a larger size is formed through photolithography requiring a relatively short time. Therefore, according to the manufacturing method, compared with the case where both of the patterns are formed through only electron beam lithography, a time required for lithography can be reduced. On the other hand, compared with the case where both of the patterns are formed through only photolithography, the forming accuracy of the first thin film pattern with a smaller size can be specifically improved.
Other and further objects, features and advantages of the invention will appear more fully from the following description.